1. Field of the Invention
This invention relates to a method for separating various contaminants form organic polymers. More particularly, this invention relates to a method of separating metal contaminants from organic polymers.
2. Prior Art
It is, of course, well known in the prior art that various metal contaminants are, frequent]y, undesirable in organic polymers and organic polymer compositions since such contaminants frequently accelerate deterioration of the polymer and may interfere with subsequent curing reactions. Metals may be introduced into the polymer either as catalyst( during polymerization or as catalyst during a subsequent treatment such as hydrogenation of an unsaturated polymer.
Heretofore several processes have been proposed for separating various metals from organic polymers. These processes generally involve reaction of the metal or a compound thereof with a reagent thereby forming a product which can then be separated. Generally, the product will be insoluble in the organic phase and may be removed therefrom either via extraction into an inorganic phase or by filtration or the like. Suitable reagents include mineral acids such as taught in U.S. Pat. No. 2,893,982 as well as carboxylic acids such as taught in U.S. Pat. Nos. 2,893,982; 3,780,138; 4,476,297 and 4,595,749. Other suitable reagents include the ammonium phosphates such as taught in U.S. Pat. Nos. 3,531,448 and 3,793,306. Carboxylic acids may be used in combination with other reagents such as an anhydrous base as taught in U.S. Pat. No. 4,028,485 or an aliphatic alcohol as taught in U.S. Pat. No. 3,780,138. An oxidizing agent may also be used prior to or simultaneously with the reagent used to react with the metal or metal compound such as tau&ht in U.S. Pat. Nos. 3,780,138; 3,793,306 and 4,595,749.
As is well known, most, if not all, of the aforementioned processes are effective in significantly reducing the amount of metal remaining in the polymer after treatment. None, however, are effective in removing all of the metal and certain of these processes frequently leave more metal in the polymer than is desired in many end uses for the polymer. Moreover, those processes involving the use of an aqueous phase generally result in higher concentrations of metal in the polymer due to entrainment of the aqueous phase in the organic, polymer phase. In light of this, the need for an improved process for separating various metals from organic polymers is believed to be readily apparent.